At present, field-effect transistors based upon gallium nitride semiconductor technology are desired by both commercial and military communication markets. The commercial communication market has particularly crowded communication bands. As such, there is a demand for highly linear field-effect transistors, especially in the millimeter wave communication bands allocated for fifth-generation (5G) cellular communications. Therefore, an unsatisfied need continually remains for highly linear field-effect transistors, and this need is particular acute for field-effect transistors based upon gallium nitride semiconductor technology.